1. Field of the Invention
The present invention relates to a reflective display device. More particularly, the present invention relates to a reflective display device using photonic crystals that improves the optical efficiency due to the selective reflection and high reflectivity of photonic crystal structures.
2. Description of the Related Art
A display device of a portable device, such as a mobile phone or a personal digital assistant (PDA), uses a reflective color display to project an image using the reflection of the surrounding light. Accordingly, there is no need for backlight in such a reflective color display, thereby making the portable device lightweight, thin, and less power consumptive.
In order to make a desired color, such reflective display devices use color filters. Therefore, the efficiency of the color filter is critical to obtaining a vivid display. A color filter produces a desired color by passing light of a particular wavelength and by absorbing light of other wavelengths. The color filter significantly affects the efficiency of the reflective display devices, since it passes only a portion of the incident white light.
FIG. 1 illustrates a sectional view of a conventional reflective display device.
The reflective display device in FIG. 1 includes a transmission type color filter 11, an optical switch 12, and a reflecting mirror 13. The optical switch 12 includes two polarizers 121, 123 and a liquid crystal layer 122 disposed between the polarizers 121, 123.
In the conventional reflective display device of FIG. 1, incident light enters the device by passing through the transmission type color filter 11, is then adjusted by the optical switch 12, is then reflected by the reflecting mirror 13, and then exits the device by passing through the transmission type color filter 11 a second time.
Such a conventional reflective display device has a problem in that light efficiency is reduced as the light passes through the transmission type color filter 11 twice, both upon entering and exiting the device. In addition, it is also problematic that the luminance and contrast are low, and the hue and brightness are not vivid.